When I got to school on Monday 17 December and checked my schedule, my heart sank to find that my homeroom lesson was to be a conversation about the Sandy Hook school shootings. Mainly because I've made an effort not to think about the details and to avoid news reports – I've taught in elementary schools and have a vivid imagination. But my heart sank for another reason: I wondered if my students in the Bronx would be nonchalant about children being shot in, for want of a better phrase, "perfect US", and I wondered how it would make me feel if they seemed unconcerned.

They weren't unconcerned of course, because they are good, compassionate kids with friends and family that they hold as dear as any other Americans do, and they can easily imagine what it is like to lose a loved one. In fact they know more about injury and death than any group of 15-year-olds should. They deal with the anxiety of living in unsafe areas every day, and have lost people they love in random acts of violence to such an extent that I have long since stopped being shocked when I hear about it. They have already lost the innocence that children, and adults, take for granted in the safe, white picket fence US where rampage shootings usually take place, the places where the first reaction is horror, but the next is: "How could this happen here?"

During our classroom discussion about Sandy Hook, one of my students asked: "How did that kid get the guns through the scanner?" Another student put him straight: "They don't scan white kids, dummy". Indeed. There's a reason why these school shootings usually happen in white, middle-class schools, and that's because white kids and adults in the US are rarely scanned when they enter a school building. I have never been scanned on entry to my building. Even when I was not known to the security guards, my white skin said: "I am a teacher" and I was never challenged. My students are scanned every day of their school lives, and if you feel demeaned and frustrated when you line up at the airport with your shoes and belt in your hands, imagine how great it feels to start everyday being treated like a potential threat to society.

The US is actually two countries: the "safe, perfect" US where terrible things don't happen, and the other US of bad neighbourhoods, guns, drugs, gangs and welfare, where the poor live; the poor who could be living in perfect US if only they just got themselves organised and stopped being so "weak, lazy, unmotivated" and, well, poor. The US is a polarised society. Rich communities are divided against poor, white communities are divided against black and brown, and the gun lobby sits happily in the middle making sure everybody stays afraid of everybody else. We are expected to fear the people who don't have what we have, and don't look like we do; but when someone "just like us" rises up to wreak a terrible vengeance on a community, we feel even more afraid. Tragedies such as Sandy Hook shock us so much because they burst the bubble that says: "I live with people just like me and we don't hurt each other." It also bursts the bubble that says: "I can keep my children safe." Imagine what it feels like to send your children to school knowing that you can't protect them as you would wish to. The parents of my students feel like this every day.

One of my students has been held at gunpoint twice in the last year, simply for playing basketball on the wrong court. Two students in my building were shot dead last year alone. Neither of these deaths was even reported in the local news. I walk past a memorial to another dead student on my way in and out of school every day. The Lord's prayer is pinned next to a photo of him in his football kit, looking ahead hopefully with his straggly, starter moustache. "We will never forget you," someone has written.

We have to stop finding the deaths of some young people more acceptable than others. To be a whole society we cannot make a distinction between the "how did this happen here" deaths and those perceived to be part of some warped natural order. Let's start to care about all the neighbourhoods, all the schools, all the beautiful little kids with their lives ahead of them and all the parents who love them. Hell, let's even start to care about the unhinged, the marginalised and the deranged, those who might come apart, take their mother's gun collection and do the worst thing it's possible to imagine; because if we don't care, there will be a lot more of them. If we do all that then maybe we can stop existing fearfully in two countries and start living hopefully in one.

Anna Bailey is a British art teacher who works at a high-poverty high school in the Bronx, New York. This is the fifth of a series: Brit in the Bronx. She writes under a pseudonym.